Modeling and optimization of biogas production from rice mill effluent using up flow anaerobic sludge blanket reactor

The main objective of the present study is to investigate the efficiency of seed sludge for the production of biogas from rice mill effluent using up flow anaerobic sludge blanket bioreactor. Response surface methodology coupled with three factors three level Box-Behnken response surface design was used to study the treatment process statistically. Effects of temperature, alkalinity dose, and flow rate on the chemical oxygen demand (COD) removal and biogas production were investigated and second order polynomial mathematical models were developed for the responses with high coefficient of determination values (R-2 > 0.99). Analysis of variance was used to evaluate the adequacy of developed mathematical models and three dimensional response surface plots were constructed to study the interactive effects of process variables on the treatment efficiency. Optimum conditions were found to be temperature of 40 degrees C, alkalinity dose of 1.5 g CaCO3/l and wastewater flow rate of 6 l d(-1). Under these conditions 87% of COD removal and biogas production of 273 ml CH4/g COD were obtained. (C) 2014 AIP Publishing LLC.